Conventionally, high integration and miniaturization of a semiconductor memory device, represented by a DRAM (Dynamic Random Access Memory), have been under way. As for the DRAM, miniaturization of a capacitor is especially important.
If, however, the capacitor is simply miniaturized, its capacitor area is reduced, and, thus, its capacitance is also reduced. Thus, in order to obtain a sufficient capacitance, many attempts have been made to increase a dielectric constant of a dielectric film of the capacitor as well as to reduce a thickness of the dielectric film.
Recently, a material having a high dielectric constant ∈ tends to be used to form the dielectric film of the capacitor. For example, Ta2O5 (∈=about 25), Al2O3 (∈=about 10), BST [=(Ba, Sr) TiO2] (∈=about 200˜500), STO [=SrTiO3] (∈=about 100˜200), and so forth are being used instead of generally utilized SiO2 (∈=about 4.1) or Si3N4 (∈=about 7˜8) (see, for example, Patent Documents 1 and 2).    Patent Document 1: Japanese Patent Laid-open Publication No. H8-195328    Patent document 2: Japanese Patent Laid-open Publication No. 2006-324363